The present invention relates to a permanent magnet type stepping motor which is driven by DC current and makes stepwise rotation, and it is particularly designed to minimize the leak of magnetic flux to the outside of the motor, so as to be used, for example, as a motor to drive the magnetic head of the magnetic disc which is in use as a peripheral instrument of electronic computers.
If the magnetic flux leaking outside from the stepping motor which drives the magnetic head is large, it gives rise to the problem of erasing the information memorized on the magnetic disc. To avoid this trouble, it is required to minimize the leaking magnetic flux generated from the motor as much as possible. In order to cope with this, conventionally a formula wherein the periphery of the motor is encircled by magnetic shield plates, or a formula wherein a magnetic plate is placed between the magnetic disc and the motor and the motor is installed on the side of the magnetic plate opposite the magnetic disc, has been employed. With these conventional formulae, however, there were such problematic points as insufficient reduction of leaking magnetic flux, requirement for an additional space; costwise, it is uneconomical as well.